Computing systems such as a portable computer (e.g., a notebook computer) rely in part on airflow through its chassis to dissipate heat generated by the various components (e.g., displays, hard drives, processors and memory) during normal operation. Additionally, when a clocked-logic component nears its maximum temperature rating, a thermal management controller of the portable computer may reduce the execution speed of the component, reducing the heat generated by the component and preserving its operability. However, cosmetic damage to the surface material of the chassis or user discomfort may occur at temperatures lower than the maximum temperature rating for most components. For example, a person whose skin may be in contact with the bottom surface of the chassis (e.g., when resting the computer on their lap) may become uncomfortable as the surface reaches 40° C., whereas many components have maximum temperature ratings that exceed 100° C.
During normal operation, airflow through the chassis prevents the outer surface from becoming too hot, even when component temperatures are at or near their maximum rating. Some systems may detect a complete failure of the system for thermal evacuation (i.e., when components are at risk of exceeding their maximum temperature ratings) by using thermistors to monitor heat-producing components or by detecting a failure of an exhaust fan.